Inch-metric dial

ABSTRACT

An inch-metric dial assembly for use in connection with a rotary drive member, comprising a first dial-bearing member mountable for rotation with the drive member, a second dial-bearing member, one of the dial-bearing members carrying a metric dial, the other an inch dial, and a geared connection effectively connected between the dial-bearing members to cause them to rotate at a predetermined ratio, the connection including a pair of gears having different numbers of teeth for attaining the ratio in a single mesh.

United States Patent 1191 Wildhaber [451 Nov. 25, 1975 INCH-METRIC DIAL [75] Inventor: Ernest Wildhaber, Rochester, N.Y.

[73] Assignee: Bird Island, Inc., Boston, Mass. [22] Filed: Sept. 20, 1973 [21] Appl. No.: 399,162

[52] US. Cl. 1l6/1l5.5; 74/804; 116/D1G. 47 [51] Int. C1. B23Q 17/00 [58] Field of Search 116/115,115.5, 124 R,

116/133, DIG. 21; 74/804, 805

[56] References Cited UNITED STATES PATENTS 2,151,534 3/1939 Scofield 116/124 R 3,043,090 7/1962 Sundt 116/124 R 3,486,386 12/1969 Laubenfels 116/115 X 3,536,030 10/1970 Schroeder... 116/ll5.5 3,536,031 10/1970 Sindall 116/1 15.5 3,568,629 3/1971 Porter 116/115.5

3,651,780 3/1972 Medhurst l16/ll5.5 3,820,501 6/1974 Foglein 116/1 15.5

FOREIGN PATENTS OR APPLICATIONS 1,133,782 11/1968 United Kingdom 116/115.5

Primary Examiner-Herbert G oldstein Assistant Examiner-Daniel M. Yasich [5 7] ABSTRACT An inch-metric dial assembly for use in connection with a rotary drive member, comprising a first dialbearing member mountable for rotation with the drive member, a second dial-bearing member, one of the dial-bearing members carrying a metric dial, the other an inch dial, and a geared connection effectively connected between the dial-bearing members to cause them to rotate at a predetermined ratio, the connection including a pair of gears having different numbers of teeth for attaining the ratio in a single mesh.

2 Claims, 7 Drawing Figures Patent Nov. 25, 1975 Sheet10f3 3,921,566

US. Patent Nov. 25, 1975 Sheet20f3 3,921,566

" U..S. P atent Nov. 25, 1975 Sheet30f3 3,921,566

FIG. 5

INCH-METRIC DIAL BACKGROUND OF THE INVENTION or others.

SUMMARY OF THE INVENTION The invention provides for simultaneous inch and metric readout, with a device that is simple, reliable, compact (especially along the screw axis), accurate, easily operated and read, and inexpensive to manufacture, and which has a minimum of backlash in the gearing.

In general, the invention features an inch-metric dial assembly for use in connection with a rotary drive member, comprising a first dial-bearing member mountable for rotation with the drive member, a second dial-bearing member, one of the dial-bearing members carrying a metric dial, the other an inch dial, and a geared coupling effectively connected between the dial-bearing members to cause them to rotate at a predetermined ratio, the coupling including a pair of gears having different numbers of teeth for attaining the ratio in a single mesh. In preferred embodiments, the two gears are mounted for rotation about parallel axes, each of the gears surrounds both the axes, the dials are concentric, and one of the gears is effectively connected to one of the dial bearing members through an eccentric coupling. In some preferred embodiments the two gears are respectively external and internal gears mounted for rotation about parallel axes, each of the gears surrounds both the axes, and the gears are constructed and arranged for meshing relative to a pitch circle of diameter larger than that of the internal gear teeth (preferably larger by at least three times the working depth of the gear teeth). In other preferred embodiments the two gears are mounted for rotation about axes that intersect at an angle differing from 180 by less than 12.

Other advantages and features of the invention will be apparent from the description of preferred embodiments thereof, and from the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an axial, section of an inch-metric dial constructed according to the invention. It applies to the conventional use of coaxial dials;

FIG. 2.is an axial view of disk 16 shown in FIG. I, showing-its engagement with the pins 30 projecting from the gear member 23;

FIG. 3 is-an axial section of another embodiment wherein each dial is coaxial with a gear of a single pair of gears that directly produces the turning ratio of the dials, in accordance with the invention;

FIG. 4 is an axial section of yet another embodiment,

where said single pair of gears have axes intersecting at an obtuse angle that differs only moderately from 180;

DESCRIPTION OF PREFERRED EMBODIMENTS In FIGS. 1 and 2 numeral 11 denotes an end plate rigidly seucred to a stationary part 12 that contains antifriction bearings 13 for mounting screw 14 and its shaft projection 15. Screw 14 engages a slide (not shown) for linearly displacing it. A disk 16 is rotatably mounted on end plate 11 coaxially with the screw 14.

A ring-shaped hub 17 is mounted on the outside of disk 16 for adjustment about axis 18, which coincides with the axis of the screw. Scale 26 on hub 17 can be set to zero at any starting position, and is held in a set position by friction. A sufficient amount of friction may be created by a plurality of balls 20 that are radially spring biased into a groove of inverted V-shape that extends about axis 18.

A member 21 with teeth 22 provided internally thereon is rigidly secured to shaft projection 15 of the screw. The internal gear member 21 meshes with an external gear 23 rotatably mounted on an eccentric projection 11a of end plate 11. This projection has an axis 18e parallel to axis 18. I

A ring-shaped hub 24 is mounted on the outside of internal gear member 2 l, for adjustment about axis 18. It is held in a set position by friction, as described for hub 17. The two hubs 17, 24 contain metric and inch scales 26, 27 respectively on their cylindrical outside surfaces. A zero mark is applied to part 12 at 26m for scale 26, and to a pointer 28, attached to part 12, at 27m for scale 27.

The single gear pair 21, 23 provides the desired ratio between the turning motions of the two scales.

The turning motion of external gear 23 is transmitted to disk 16 at a one-to-one ratio: Four cylindrical pins 30 are secured to gear 23, with the pin axes parallel to the axis 18s of the gear. They engage circular holes 31 provided in disk 16 (see FIG. 2). The diameter of the holes 31 exceeds the diameter of the pins by double the eccentricity of axis 182 from axis 18. In this way the pins transmit to disk 16 the exact turning motion of gear 23, at a one-to-one ratio. This drive can be considered an eccentric coupling. It permits use of coaxial scales.

Conventional involute tooth design for tooth numbers such as for instance 127/ would result in what is known as internal interference and thus be impractical. However by designing the gears for pitch circles substantially larger in diameter (preferably by at least three times the working tooth depth) than the internal gear teeth, and by using reduced tooth depth the design becomes feasible even with involute teeth. The pitch circles are understood to be the imaginary circles of the two gears that roll on each other Without sliding. The mesh then occurs at'much distance from the axis of instantaneous relative motion (the instant axis). Tooth sliding increases in proportion to the distance of the tooth contact from the instant-axis. However because of the internal mesh with nearly equal tooth numbers, sliding is still moderate and well acceptable, especially where almost no power is transmitted.

Screw 14 is turned by gripping handle 33 and turning it about axis 18. As the lead of the screw is preferably kept small, it takes often a large number of turns to move the slide 'to a desired position. To facilitate counting the number of turns of scale 26, a knob or button 34 is provided and set to protrude slightly over the adjacent smooth outside surface of hub 17: The number of full turns of scale 26 can then be measured by touch. This is especially desirable on scale 26 whose turns differ from the turns of the handle 33.

The embodiment of FIG. 3 uses the same mesh between internal gear 42 and mating external gear 43, as described for gears 21, 23. Here, however, one scale, scale 46 is coaxial with the external gear 43, simplifying the design by omission of the eccentric coupling. That is, the two scales 46, 47 are coaxial with axes 18e and 18 respectively, rather than being coaxial with each other. Otherwise the design is along the lines already described. Hubs 37'and 44 are mounted on the body of external gear 43 and of internal gear 42 respectively, foradjustment about the axes of the respective gears.

In the embodiments of FIGS 4-7 the two gears that provide the final ratio between the two scales have intersecting axes. Their axes intersect at an angle that differs from l80'degrees by less than twelve degrees. FIG. 4 shows a 4 difference 49 for a tooth ratio of 127/125. 50 denotes the intersection point of the axes 51, 52 of the two mating gears 53,54 of FIG. 4, and of the two gears 55, 56 of FIG. 6. 57 is the instant axis for the above tooth ratio. The teeth 53, 54 of gears 53, 54, and the teeth 55', 56 of gears 55, 56 (FIG. 6) are free from the restrictions of internal-external mesh. The tooth depth is not limited thereby. The tooth profiles are practically straight. At least the center of the teeth can be placed on the instant axis 57, so that tooth sliding is practically zero. Also the teeth mesh at the region of deepest penetration.

Conventional teeth would extend along the instant axis 57. This would result in a markedly internal bevel gear 53 or 55. Preferably the gears 53, 55 are made flat gears or crown gears at least approximately. Either their root surface is a plane perpendicular to the gear axis'51, or the face surface of their teeth is a plane. This adds to the simplicity. And it has no drawback. In any case the tooth-side surfaces of the gears 53, 55 may be made planes.

A knob or button may be used with this design, as described for the previous embodiments.

The embodiment of FIG. 6 omits the adjustable hubs, parts 73, 74. The displacement is measured from a fixed position, as indicated by diagram FIG. 7.

' In FIG. 7 80 denotes the entire dial, 81 the stationary part that holds the bearings. Screw 60 engages slide 82. The linear inch and metric scales 83, 84, respectively, start at an end position of slide 82. The displacement from the end position is measured by a mark 85 directly on the slide, reading scale 83, and by a mark 86 placed on a pointer 87 rigid with the slide. The two marks are offset from one another, unless a transparent pointer 87 is used.

The linear scales 83, 84 also provide a check for the number of turns used.

End plate 62 has a cylindrical projection 64' coaxial with axis 52 and a plane side surface 65 at right angles thereto. Gear 56 is mounted thereon. It meshes with gear-55 that is rigid with screw 60. The scales are applied at 90 and 91 togears 55, 56 respectively. A thin cylindrical tube 92 is secured to end plate 62. It encloses, the dial mechinism. If made of metal, the marks are applied at 92',92" on the inclined sides of an opening at the top of the tube. If made of transparent plastic, the opening is dispensed with, and the marks are on the inside surface of the tube.

Gear 55 is rotated with a handle 94 that is counterbalanced by a weight 95.

In both FIG. 4 and FIG. 6 numeral 60 denotes the screw, of which only the extension is visible. This end is rotatably mounted in antifriction bearings 61. End plates 62, 62 secure the bearings axially in the stationary head 63.

End plate 62 (FIG. 4) has a cylindrical projection 64 coaxial with axis 52 and a plane shoulder surface 65 perpendicular thereto. Gear 54 is rotatable on these surfaces. Its teeth 54' mesh with the teeth 53' of gear 53. Gear 53 is keyed to the extension of screw 60. A nut 66 keeps the hub of gear 53 and sleeve 67 pressed against the inner race of the adjacent bearing 61. Gear 53, and through it screw 60, may be turned with handle 68 that is secured thereto. A counter-weight 70 balances the handle.

The scales 71, 72 are applied to the cylindrical outside surfaces of ring-shaped hubs 73, 74. These parts are mounted on the cylindrical outside surfaces of the gears 53, 54 respectively, for adjustment about the gear axes. Multiple balls are pressed outwardly by springs into a circular groove of inverted V-shape, to secure said parts axially and to provide enough friction to maintain said parts in a set place, as described in connection with FIGS. 1 to 3.

A zero mark for scale 71 is applied to a pointer 76,

while end plate ,62 contains the zero mark 77 for scale 72 (FIG. 5).

Hub 73 has a lateral projection 73a with spherical outside surface centered at 50. Hub 74 has a lateral projection 74a with a spherical inside surface that matches the spherical outside surface of projection 73a. In operation the matching spherical surfaces move relatively to each other about center 50, while sealing off the inside of the dial.

A knob or button 96 is secured to gear 56. It extends into a circular groove 97 provided on end plate 62'. The groove extends about axis 52 and has some clearance with the knob. The means represented by knob or button 96 impact at every turn with an approximately stationary portion represented by ball 98. The ball 98 is pressed forward by a spring, to effect an impact between knob and ball, an impact with a resilient member. This impact produces a slight click. The number of turns of gear 56 and its scale may then be counted by the numberof such clicks, rather than by touch.

The gears may be coined or pressed, and made of either metal or a suitable plastic.

The use of a single mesh of a pair of gears to attain the desired dial ratio minimizes backlash in the gearing between the dials. In the embodiments of FIGS. l3,

the effect of the small amount of remaining backlash upon the dials is further minimized by the fact that the gear teeth mesh at a diameter close to that of the dials.

A brief operating description of the various embodiments is: In the embodiments of FIGS. 1, 3, 4, and 6, the turning motions of the handle are transmitted directly to one dial, and through the single gear mesh to the other dial, causing the two dials to rotate at different rates having an exact inch-metric ratio. In FIG. 1 an eccentric coupling allows the scales to be coaxial. In FIG. 3 the scales are non-coaxial and are read at their common tangent plane. In FIGS. 4 and 6 the scales have intersecting axes.

Subject matter disclosed herein relating to noncoaxial dials is the joint invention of Ernest Wildhaher and Howard G. Chapman, claimed in application Ser. No. 399,163, filed Sept. 20, 1973. Subject matter disclosed herein relating to counting dial turns by impact is the joint invention of Paul V. Murray and Philip E. Przymierski, claimed in application Ser. No. 399,161, filed Sept. 20, 1973, now abandoned.

Other embodiments are within the following claims:

I claim:

1. An inch-metric dial assembly for use in connection with a rotary drive member, comprising a first dial-bearing member mountable for rotation with said drive member,

a second dial-bearing member,

one of said dial-bearing members carrying a metric dial, the other an inch dial, and

a geared connection effectively connected between said dial-bearing members to cause them to rotate at a predetermined ratio such as to cause said dials to respectively indicate metric and inch measurements exactly corresponding to the rotation of said drive member, said connection including a single pair of gears having different numbers of teeth for attaining said ratio in a single mesh, one of said gears having 127 teeth, the other of said gears having either 125 or teeth,

said gears being respectively internal and external gears mounted for rotation about spaced parallel axes with each of said gears surrounding both said axes, said gears being constructed and arranged for meshing relative to a pitch circle of diameter larger than the diameter of the internal gear teeth.

2. The assembly of claim 1 wherein said pitch circle diameter is larger than the diameter of said internal gear teeth by at least three times the working depth of the teeth of said gears. 

1. An inch-metric dial assembly for use in coNnection with a rotary drive member, comprising a first dial-bearing member mountable for rotation with said drive member, a second dial-bearing member, one of said dial-bearing members carrying a metric dial, the other an inch dial, and a geared connection effectively connected between said dialbearing members to cause them to rotate at a predetermined ratio such as to cause said dials to respectively indicate metric and inch measurements exactly corresponding to the rotation of said drive member, said connection including a single pair of gears having different numbers of teeth for attaining said ratio in a single mesh, one of said gears having 127 teeth, the other of said gears having either 125 or 120 teeth, said gears being respectively internal and external gears mounted for rotation about spaced parallel axes with each of said gears surrounding both said axes, said gears being constructed and arranged for meshing relative to a pitch circle of diameter larger than the diameter of the internal gear teeth.
 2. The assembly of claim 1 wherein said pitch circle diameter is larger than the diameter of said internal gear teeth by at least three times the working depth of the teeth of said gears. 